Semiconductor laser arrays typically comprise a plurality of semiconductor injection lasers which are formed on a planar substrate. Radiation is, in certain devices, emitted from the device surface such that the optical axis of the radiation is typically about perpendicular to the plane of the substrate. In forming a laser array it is typically desirable that the lasers be phase-locked so that the output of each of the lasers is coherent with that of the others and the array behaves as a single light source. Evanescent coupling is one technique which provides phase locking between adjacent parallel devices. However, this technique is limited in that radiation coupling usually occurs only between next adjacent neighbors. Other array arrangements include linear arrays formed by coupling a portion of a first device's output into a second device's input which is aligned with the optical output of the first device. This latter arrangement is limited to a one-dimensional array.
The present inventors recognize it would be desirable to form a two-dimensional array of lasers which may be locked in phase wherein the devices may be organized into one or more arrays such that all devices are radiation coupled without being next adjacent neighbors or solely linearly aligned so that more devices may be efficiently coupled in a relatively smaller region of the substrate.
A light coupling system according to the present invention for coupling radiation emitted by a semiconductor radiation emitting device comprises a substrate having a broad planer surface. An optical grating comprising a plurality of spaced nodules overlies the substrate broad surface. The grating is adapted to receive the emitted radiation along an optical axis lying in a plane parallel to the plane of the broad surface. The nodules are arranged in a grid and so positioned that a first portion of the received radiation reflects from the grating in a direction along the optical axis and a second portion of the received radiation is deflected by the grating in a second direction different than the first direction. As a result, multiple radiation emitting devices adapted to process radiation received thereby may be coupled for providing phase-locking of the radiation emitted by the devices.